U.S. patent number 6,546,174 [Application Number 09/756,104] was granted by the patent office on 2003-04-08 for long length, side-emitting fiber optic cables.
This patent grant is currently assigned to Polymicro Technologies, LLC.. Invention is credited to James P. Clarkin.
United States Patent |
6,546,174 |
Clarkin |
April 8, 2003 |
Long length, side-emitting fiber optic cables
Abstract
An extended length side emitting cable is disclosed. The cable
includes transmitting and side emitting fibers. As light proceeds
along the side emitting fibers, it decreases in intensity and in
color quality. The transmitting fibers are coupled into the side
emitting fibers to refresh the light. In this manner the cable
maintains increased uniformity of color and intensity along its
length.
Inventors: |
Clarkin; James P. (Scottsdale,
AZ) |
Assignee: |
Polymicro Technologies, LLC.
(Phoenix, AZ)
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Family
ID: |
25042057 |
Appl.
No.: |
09/756,104 |
Filed: |
January 9, 2001 |
Current U.S.
Class: |
385/100; 362/559;
385/109 |
Current CPC
Class: |
G02B
6/001 (20130101); G02B 6/443 (20130101) |
Current International
Class: |
F21V
8/00 (20060101); G02B 6/44 (20060101); G02B
006/44 () |
Field of
Search: |
;385/100,99,98,95,109,901 ;362/556,559,565,576,582 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
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PCT WO 98/45645 |
|
Oct 1998 |
|
WO |
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Primary Examiner: Feild; Lynn D.
Assistant Examiner: Hyeon; Hae Moon
Attorney, Agent or Firm: Pillsbury Winthrop LLP
Claims
What is claimed is:
1. A hybrid optical fiber cable, comprising: a first side-emitting
illumination optical fiber; a second side-emitting illumination
optical fiber, a first end thereof displaced longitudinally from a
first end of the first side-emitting illumination optical fiber by
a distance such that the optical fiber cable retains sufficient
chromaticity to obtain a predetermined lighting effect; and a first
low attenuation optical fiber, optically coupled to the first end
of the second side-emitting illumination optical fiber.
2. A cable as in claim 1, further comprising: a strength member,
disposed around the optical fibers, the strength member allowing
light emitted by the side-emitting illuminating optical fibers to
pass therethrough.
3. A cable as in claim 2, further comprising: an outer jacket,
disposed around the optical fibers and the strength member, the
outer jacket allowing light emitted by the side-emitting
illuminating optical fibers to pass therethrough.
4. A cable as in claim 1, wherein the first end of the second
side-emitting optical fiber is displaced longitudinally from the
first end of the first side-emitting optical fiber by a distance
greater than about 25 feet.
5. A cable as in claim 1, further comprising a light source,
optically coupled into a second end of the first side-emitting
illumination optical fiber and into the first low attenuation
optical fiber and optically coupled via the first low attenuation
optical fiber to the first end of the second side-emitting
illumination optical fiber.
6. A cable as in claim 1, further comprising a third side -emitting
illumination optical fiber, a first end thereof displaced
longitudinally from the first end of the first side-emitting
illumination optical fiber and the first end of the second
side-emitting illumination optical fiber; and a second low
attenuation optical fiber, optically coupled to the first end of
the third side-emitting illumination optical fiber.
7. A cable as in claim 6, further comprising a light source,
optically coupled into the first end of the first side-emitting
illumination optical fiber and into the first and second low
attenuation optical fibers and optically coupled via the first low
attenuation optical fiber to the first end of the second
side-emitting illumination optical fiber and via the second low
attenuation optical fiber to the first end of the third
side-emitting illumination optical fiber.
8. An illumination device, comprising: a first side-emitting
illumination optical fiber having a first end optically coupled to
a light source; a second side-emitting illumination optical fiber,
a first end thereof displaced longitudinally from a second end of
the first side-emitting illumination optical fiber by a distance
such tat the illumination device retains sufficient chromaticity to
obtain a predetermined lighting effect; and a low attenuation
optical fiber, a first end thereof optically coupled to the light
source, a second end thereof optically coupled to the first end of
the second side-emitting illumination optical fiber.
9. A hybrid optical fiber cable, comprising: a first side-emitting
illumination optical fiber; a second side-emitting illumination
optical fiber, a first end thereof displaced longitudinally from a
second end of the first side-emitting illumination optical fiber
such that the optical fiber cable retains at least one of uniform
intensity and uniform chromaticity to obtain a predetermined
lighting effect; and a low attenuation optical fiber optically
coupled to the first end of the second side-emitting illumination
optical fiber.
10. A cable as in claim 9, further comprising: a strength member,
disposed around the optical fibers, the strength member allowing
light emitted by the side-emitting illuminating optical fibers to
pass therethrough.
11. A cable as in claim 10, further comprising: an outer jacket,
disposed around the optical fibers and the strength member, the
outer jacket allowing light emitted by the side-emitting
illuminating optical fibers to pass therethrough.
12. A cable as in claim 9, wherein the first end of the second
side-emitting optical fiber is displaced longitudinally from the
first end of the first side- emitting optical fiber by a distance
greater than about 25 feet.
13. A cable as in claim 9, further comprising a light source,
optically coupled into a second end of the first side-emitting
illumination optical fiber and into the first low attenuation
optical fiber and optically coupled via the first low attenuation
optical fiber to the first end of the second side-emitting
illumination optical fiber.
14. A cable as in claim 9, further comprising a third side-emitting
illumination optical fiber, a first end thereof displaced
longitudinally from the first end of the first side-emitting
illumination optical fiber and the first end of the second
side-emitting illumination optical fiber; and a second low
attenuation optical fiber, optically coupled to the first end of
the third side-emitting illumination optical fiber.
15. A cable as in claim 14, further comprising a light source,
optically coupled into the first end of the first side-emitting
illumination optical fiber and into the first and second low
attenuation optical fibers and optically coupled via the first low
attenuation optical fiber to the first end of the second
side-emitting illumination optical fiber and via the second low
attenuation optical fiber to the first end of the third
side-emitting illumination optical fiber.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to fiber optic cables. More
particularly, the present invention relates to extended length
side-emitting fiber optic cables.
2. Background of the Invention
Side-emitting optical cables are available which can accept light
from a point source and distribute it along a linear path for area
illumination. One variation of side-emitting optical cables makes
use of a series of notches in the optical fiber, each notch having
a surface angled to the axis of the fiber. The angled surface
reflects a portion of the light out of the fiber, making it
available for use, either to be coupled into several output fibers,
or more generally, into free space. Alternatively, an optical fiber
may contain regions having differing indices of refraction so as to
refract light out of a side of the optical fiber at various
locations along the fiber's length. Another method makes use of
reflective or refractive particles distributed throughout an
optical fiber, causing scattering of light. The scattered light
escapes through the side of the fiber.
Yet another method of providing side-emitting fibers is to make use
of all-plastic fibers which have an outer jacket which allows
transmission of light radiated continuously along the length of the
fiber. This type of fiber is provided for markets such as
landscaping, architecture and pool lighting, for example.
Since plastic fibers are flexible in comparison to silica fibers,
they may be manufactured in larger diameters without increasing
risk of damage from bending. Further, plastic fibers generally have
a large numerical aperture (NA) compared to silica fibers. This
combination makes plastic fibers well suited to use with large or
diffuse light sources which might be difficult to couple into
small, low NA silica fibers. Thus, plastic fibers are a good choice
when working in area lighting applications which do not require the
precision available with silica fibers.
Plastic fibers have two important limitations, however, when used
in outdoor applications. The first is that they tend to have
relatively high attenuation in the visible light spectrum, on the
order of hundreds or thousands of dB/km, compared to available
silica core fibers having attenuations below one dB/km. The second
limitation results from a spectrum dependent transmittance. When
white light is injected into a conventional plastic fiber, red
light is absorbed at a greater rate than shorter wavelength blue
light. Thus, as the light travels along the fiber the light becomes
more and more blue, resulting in a blue tint to light emitted from
the side of the fiber at points furthest from the light source.
This has the obvious disadvantage that over long distances,
side-emitting plastic fibers are not well suited to situations
requiring a true color light source. These two limitations result
in an effective length for an all-plastic illumination fiber of
less than about 100 feet.
While silica core fibers are well adapted to providing long
transmission distances, having low attenuation and good spectral
performance, they are not well suited to use as side-emitting
fibers and are thus, not presently a good choice for area lighting
applications.
SUMMARY OF THE INVENTION
The present invention addresses the needs identified above by
providing a hybrid optical fiber cable, which includes a first
side-emitting illumination optical fiber and a second side-emitting
illumination optical fiber. A first end of the second side-emitting
illumination optical fiber is displaced longitudinally from a first
end of the first side-emitting illumination optical fiber. A
transmitting optical fiber is optically coupled to the first end of
the second side-emitting illumination optical fiber to produce good
spectral performance and long transmission distances in a fiber
cable which provides side-emitted light.
In another embodiment, a strength member is disposed around the
optical fibers and allows light emitted by the side-emitting
illuminating optical fibers to pass therethrough.
In yet another embodiment, an outer jacket is disposed around the
optical fibers and the strength member. As with the strength
member, the outer jacket allows light emitted by the side-emitting
illuminating optical fibers to pass therethrough.
In another embodiment, the first end of the second side-emitting
optical fiber is displaced longitudinally from the first end of the
first side-emitting optical fiber by a distance greater than about
25 feet.
In another embodiment of the present invention the first end of the
second side-emitting optical fiber is displaced longitudinally from
the first end of the first side-emitting optical fiber by a
distance such that the optical fiber cable retains sufficient
chromaticity to obtain a predetermined lighting effect.
In an alternate embodiment of the present invention, a light source
is optically coupled into the first end of the first side-emitting
illumination optical fiber and into the first low attenuation
optical fiber and optically coupled via the first low attenuation
optical fiber to the first end of the second side-emitting
illumination optical fiber.
Another embodiment includes a third side-emitting illumination
optical fiber. A first end of the third side-emitting fiber is
displaced longitudinally from the first end of the first
side-emitting illumination optical fiber and the first end of the
second side-emitting illumination optical fiber. A second low
attenuation optical fiber is optically coupled to the first end of
the third side-emitting illumination optical fiber. This embodiment
may further include a light source optically coupled into the first
end of the first side-emitting illumination optical fiber and into
the first and second low attenuation optical fibers and optically
coupled via the first low attenuation optical fiber to the first
end of the second side-emitting illumination optical fiber and via
the second low attenuation optical fiber to the first end of the
third side-emitting illumination optical fiber.
Additionally, the present invention may be embodied in an
illumination device, including a first side-emitting illumination
optical fiber having a first end optically coupled to a light
source, a second side-emitting illumination optical fiber, a first
end thereof displaced longitudinally from the first end of the
first side-emitting illumination optical fiber, and a low
attenuation optical fiber, a first end thereof optically coupled to
the light source, a second end thereof optically coupled to the
first end of the second side-emitting illumination optical
fiber.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute
a part of this specification illustrate an embodiment of the
invention and together with the description, explains the objects,
advantages, and principles of the invention.
FIG. 1 shows a cross-section of an optical fiber cable according to
an embodiment of the present invention.
FIG. 2 is a schematic representation of an optical fiber cable
according an embodiment of the present invention, showing cross
connected transmitting and side-emitting fibers.
FIG. 3 is a schematic representation of an optical fiber cable
according to an embodiment of the present invention, showing
staggered coupling between transmitting and side-emitting
fibers.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the following description, for purposes of explanation and not
limitation, specific details are set forth such as particular
optical and electrical components, techniques, etc. in order to
provide a thorough understanding of the present invention. However,
the invention may be practiced in other embodiments that depart
from these specific details. In some instances, detailed
descriptions of well-known devices may be omitted so as not to
obscure the description of the present invention with unnecessary
details. Throughout the specification, where reference is made to a
single fiber, a bundle of fibers may be understood as being
equivalent.
Referring now to FIG. 1, an optical fiber cable 10 is shown. The
optical fiber cable 10 contains several transmitting optical fibers
12. The transmitting optical fibers 12 are preferably low
attenuation fibers and more specifically are preferably silica core
fibers and may have a plastic or silica cladding. Included in the
cable are several side-emitting optical fibers 14 which are
preferably all-plastic fibers, though other side-emitting optical
fibers may be used. A filler member 16 can be included to provide
an improved packing arrangement and may be located in the center
for the arrangement shown, or in another location if a different
fiber arrangement is selected. The filler member 16 can
additionally perform as a strengthening member and could be, for
example, a steel wire.
Preferably, a strength member 18 surrounds the fibers, holding them
in place and providing additional strength to the cable 10. The
strength member 18 should be reasonably transparent or have holes
or be otherwise configured so as to avoid blocking the light
emitted from the side-emitting fibers 14. The strength member may
advantageously be an aramid yarn, for example, though any
appropriate material may be used. The cable 10 further has an outer
jacket 20 which contains the fibers 12, 14, filler 16 and strength
member 18. The outer jacket 20 should also allow light to pass
through at least portions thereof. For example, the outer jacket 20
may be a transparent polyvinyl chloride (PVC) material. While for a
continuous light source, the entire outer jacket 20 should be
substantially transparent, alternately it could have opaque and
transparent portions, providing light from discrete portions of the
cable's length.
Referring now to FIG. 2, one embodiment of a cable 10 according to
the present invention is shown. Several transmitting fibers 12, are
placed alongside a first group of side-emitting fibers 14. One end
of each of the transmitting fibers 12 is coupled with a splice or a
coupler 22 to a member of a second group of side-emitting fibers
14'. Though the coupling shown is a one-to-one coupler, any
suitable coupling or splice could be used. The second group of
side-emitting fibers 14' extends further along the length of the
cable 10. In FIG. 2, the coupling region is shown with a sleeve 24
provided to relieve strain. The sleeve 24 is further protected by a
protective shrink wrap 26. The sleeve 24 may be steel, for example,
and the shrink wrap 26 may be made from an appropriate plastic
material. While the sleeve 24 and shrink wrap 26 are not necessary,
they do improve the durability of the cable 10.
In operation, the cable 10 shown in FIG. 2 accepts light from a
light source at the left, not shown. The light source may be any
appropriate light source such as an LED, laser, light bulb, laser
diode, etc. Light is injected into the side-emitting fibers 14 and
the transmitting fibers 12. The light travels along the length of
the fibers 12, 14 and is emitted from the sides of the
side-emitting fibers. As the light travels further from the light
source in the side-emitting fibers, it tends to change color due to
wavelength dependent scattering and attenuation. Further, the
overall power is attenuated. At a particular distance from the
light source, the light traveling in the side-emitting fibers 14
will no longer be suitable for the selected application. For an
area illumination application, this distance will typically be on
the order of 25 to 100 feet. At, or preferably before, that
distance, the transmitting fibers 12, which will have lost only a
small fraction of their power, are coupled into a second group of
side emitting fibers 14'. The second group of side-emitting fibers
14' transmit the light received from the transmitting fibers 12 and
emit light from their sides over a distance similar to that
provided by the first group of side emitting fibers 14. The length
of each segment of fiber is preferably selected such that chromatic
distortion and attenuation are not so great as to detract from the
desired lighting effect. As may be understood, the particular
application will define the allowable chromatic distortion and
attenuation. In the case where an area, such as a landing pad,
merely must be marked visibly, chromaticity will be relatively
unimportant, and the attenuation will be of greater importance. In
contrast, in an application such as architectural lighting, both
chromaticity and attenuation are likely to be important in order to
achieve a uniform effect.
Referring now to FIG. 3, another coupling arrangement is shown. In
this arrangement, several transmitting fibers 12 extend into the
cable and each is coupled to a side-emitting fiber 14. The
staggered coupling arrangement allows for greater uniformity of the
light intensity emitted from the sides of the cable. In contrast to
the embodiment illustrated in FIG. 2, there is not a single point
along the length of the cable where light traveling in the
side-emitting fibers 14 is refreshed, but rather many. Thus, any
bright spots are distributed instead of concentrated at a single
junction area.
FIG. 3 specifically shows three side-emitting illumination optical
fibers 14, each having a first end thereof displaced longitudinally
from one another. Two low attenuation optical fibers 12 are
optically coupled to the first end of a second side-emitting
illumination optical fiber 14 and to a first end of a third
side-emitting illumination optical fiber 14, respectively.
In FIG. 1 as shown, there are six side-emitting fibers 14 and
twelve transmitting fibers 12 along with a single filler member 16.
This arrangement could be used, for example, to triple the possible
effective cable length. As light proceeds along the length of the
cable 10 and the first six side-emitting optical fibers 14 begin to
suffer from attenuation, six of the transmitting optical fibers 12
are coupled into the side-emitting optical fibers 14 or into ends
of a second group of side-emitting optical fibers (not shown).
Proceeding further along the length of the cable 10, the
side-emitted signal again begins to decay and a second coupling
using the remaining six transmitting fibers 12 refreshes the
side-emitted signal once more. By mirroring this arrangement and
providing a light source at either end of the cable 10, a cable
having a length six times longer than a non-hybrid cable may be
manufactured while maintaining light quality and intensity.
The 19 fiber arrangement also makes use of the fact that 19 fibers
(18 light guiding fibers and one strength member) can be
close-packed across the face of the cable. Likewise seven fibers
may be close packed, a hexagon of fibers packed around a single
strength member. In a seven fiber cable, four light transmitting
fibers could be used alongside two side-emitting fibers to produce
a hybrid cable three times as long as a conventional side-emitting
cable.
As is apparent, many other arrangements are possible. By way of
example, in a 19 fiber cable, three fibers may be side-emitting
while 15 are transmitting fibers. At each junction, three of the
transmitting fibers may be coupled to three side-emitting fibers,
allowing five extensions, and a cable six times as long as a
conventional side-emitting cable. Again, by mirroring the cable and
providing a second light source, a cable twice again as long
(twelve times as long as a conventional cable) may be produced. One
skilled in the art may recognize many alternate arrangements.
While the invention has been described in connection with what is
presently considered to be the most practical and preferred
embodiment, it is to be understood that the invention is not
limited to the disclosed embodiment, but on the contrary it is
intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the claims which
follow.
* * * * *